Liquid Electrolyte Dye-sensitized Solar Cells Research Articles

Effective redox shuttles for polymer gel electrolytes-based quasi-solid-state dye-sensitized solar cells in outdoor and indoor applications: Comprehensive comparison and guidelines

Various redox shuttle-mediated polymer gel electrolytes (PGEs) were utilized individually to fabricate quasi-solid-state (QSS) dye-sensitized solar cells (DSSCs) for outdoor and indoor applications. The power conversion efficiency (PCE) of QSS DSSCs based on I3−/I−-mediated PGEs was comparable with liquid electrolyte-devices under both 1-sun and 1000 lux compact fluorescent light (CFL) (compact fluorescent lamp) illuminations. The PCEs for QSS-DSSCs based on cobalt/copper complex-mediated PGEs were not comparable with their liquid electrolyte DSSCs under 1-sun condition, but, comparable, even higher for cobalt complex-mediated PGE devices, under CFL light. The PCE for organic dye-sensitized cobalt PGE devices was in the range of 23%–30% under 200–2000 lux CFL illuminations. The remarkable PCEs of 27.5% and 25.0% were obtained for cobalt and copper complex-mediated PGE-based QSS DSSCs using organic sensitizers, respectively, under 1000 lux CFL light. This result specifies that the mass transport limitation of Co-/Cu-complexes in PGEs can only be applicable for 1-sun illumination, not for ambient lighting. The outstanding efficiency under CFL ambient light and high stability under 50 °C make us optimistic for future commercial utilization of metal-complex-mediated PGE-QSS DSSCs as a safe power source for the internet of things and low-powered autonomous electronic devices.

Redox Shuttle-Based Electrolytes for Dye-Sensitized Solar Cells: Comprehensive Guidance, Recent Progress, and Future Perspective.

A redox electrolyte is a crucial part of dye-sensitized solar cells (DSSCs), which plays a significant role in the photovoltage and photocurrent of the DSSCs through efficient dye regeneration and minimization of charge recombination. An I-/I3 - redox shuttle has been mostly utilized, but it limits the open-circuit voltage (V oc) to 0.7-0.8 V. To improve the V oc value, an alternative redox shuttle with more positive redox potential is required. Thus, by utilizing cobalt complexes with polypyridyl ligands, a significant power conversion efficiency (PCE) of above 14% with a high V oc of up to 1 V under 1-sun illumination was achieved. Recently, the V oc of a DSSC has exceeded 1 V with a PCE of around 15% by using Cu-complex-based redox shuttles. The PCE of over 34% in DSSCs under ambient light by using these Cu-complex-based redox shuttles also proves the potential for the commercialization of DSSCs in indoor applications. However, most of the developed highly efficient porphyrin and organic dyes cannot be used for the Cu-complex-based redox shuttles due to their higher positive redox potentials. Therefore, the replacement of suitable ligands in Cu complexes or an alternative redox shuttle with a redox potential of 0.45-0.65 V has been required to utilize the highly efficient porphyrin and organic dyes. As a consequence, for the first time, the proposed strategy for a PCE enhancement of over 16% in DSSCs with a suitable redox shuttle is made by finding a superior counter electrode to enhance the fill factor and a suitable near-infrared (NIR)-absorbing dye for cosensitization with the existing dyes to further broaden the light absorption and enhance the short-circuit current density (J sc) value. This review comprehensively analyzes the redox shuttles and redox-shuttle-based liquid electrolytes for DSSCs and gives recent progress and perspectives.

A Review on Gel Polymer Electrolytes for Dye-Sensitized Solar Cells.

Significant growth has been observed in the research domain of dye-sensitized solar cells (DSSCs) due to the simplicity in its manufacturing, low cost, and high-energy conversion efficiency. The electrolytes in DSSCs play an important role in determining the photovoltaic performance of the DSSCs, e.g., volatile liquid electrolytes suffer from poor thermal stability. Although low volatility liquid electrolytes and solid polymer electrolytes circumvent the stability issues, gel polymer electrolytes with high ionic conductivity and enduring stability are stimulating substitutes for liquid electrolytes in DSSC. In this review paper, the advantages of gel polymer electrolytes (GPEs) are discussed along with other types of electrolytes, e.g., solid polymer electrolytes and p-type semiconductor-based electrolytes. The benefits of incorporating ionic liquids into GPEs are highlighted in conjunction with the factors that affect the ionic conductivity of GPEs. The strategies on the improvement of the properties of DSSCs based on GPE are also presented.

Investigation of Aloe Vera Latex Used as Natural Dye in TiO2-Based Heterojunction and Liquid-Electrolyte Dye-Sensitized Solar Cells

Abstract The use of naturally extracted compounds as dye sensitizers is a very promising alternative for the manufacture of low-cost solar cells. These directly convert solar energy to electricity. In the present study, aloe latex solid (ALS), which is an orange-yellow solid compound extracted from aloe vera leaves, was deposited on a TiO2 thin film (TiO2/ALS) for the construction of two different solar cell configurations. The UHPLC-DAD-ESI-MS analysis, UV–Vis, and FTIR spectroscopic studies were performed for the prepared dye sensitizer. In fact, the performance of the TiO2/ALS composite was investigated in a heterojunction dye-sensitized solar cell (HJ-DSSC) and a liquid-electrolyte-based dye-sensitized solar cell (LE-DSSC) to identify the architecture with the highest efficiency of sunlight conversion. The solar cells’ photovoltaic performance in terms of short-circuit current, open-circuit voltage, fill factor, and energy conversion efficiency was tested with photocurrent density–voltage measurements. Interesting solar conversion efficiencies were obtained for both architectures with a maximum value of about 1.17% corresponding to the LE-DSSC configuration.

The Effect of Difference Molar Ratios of Dibromo-EDOT as Hole Transporting Material for Solid State Dye-Sensitized Solar Cells

The dye-sensitized solar cells (DSSCs) are one of the promising organic photovoltaic cells due to their low cost, flexibility, and relatively good efficiency. Nevertheless, utilization of liquid electrolyte in DSSCs brings practical problems for commercialization, which leads to solid-state dye-sensitized solar cells (ssDSSCs), that based on organic conducting polymers or inorganic p-type semiconductors as hole transport materials (HTM). A one-side ssDSSCs fabricated here, with a conductive polymer Dibromo-EDOT as an HTM, and also check ssDSSCs efficiency by variation of the HTM concentrations. The morphology of cells examined through SEM, and intensity-modulated photocurrent/voltage spectroscopy, measurements were used to elucidating the electrochemical properties of ssDSSCs. We also optimize the blocking layer thickness and different molar ratios of HTM for the best efficient ssDSSCs.

Characterization of poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) nanofiber membrane based quasi solid electrolytes and their application in a dye sensitized solar cell

The electrolyte plays a major role in dye sensitized solar cells (DSSCs). In this work a quasi-solid state (gel) electrolyte has been formed by incorporating a liquid electrolyte made with KI dissolved in ethylene carbonate (EC) and propylene carbonate (PC) co-solvent in poly (vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) co-polymer nanofiber membrane prepared by electrospinning. SEM images of the electrolyte membrane showed the formation of a three-dimensional network of polymer nanofibers with diameters between 100 and 300 nm and an average membrane thickness of 14 μm. The electrolyte was characterized by FTIR and differential scanning calorimetry (DSC) measurements. The DSSCs fabricated with this electrolyte were characterized by current-voltage and Electrochemical Impedance Spectroscopy (EIS) measurements. DSC thermograms revealed that the crystallinity of the PVdF-HFP nanofiber is 14% lower than that of the pure PVdF-HFP polymer while the FTIR spectra showed a reduced polymer-polymer interaction in the nano fiber based gel electrolyte. The DSSCs fabricated with nanofiber based gel electrolyte showed an energy conversion efficiency of 5.36% under 1.5 a.m. solar irradiation, whereas the efficiency of the DSSC made with the liquid electrolyte based cell was 6.01%. This shows the possibility of replacing the liquid electrolyte in DSSCs by electro-spun polymer nanofiber based gel electrolyte and thereby minimizing some major drawbacks associated with liquid electrolyte based solar cells while maintaining a reasonably high efficiency.

Study of quasi-solid electrolyte in dye-sensitized solar cells using surfactant as pore-forming materials in TiO2 photoelectrodes

A novel polymer gel electrolyte was used to improve the performance and long-term stability in dye-sensitized solar cells (DSSCs). The polymer gel electrolyte (PGE) was prepared by mixing 5 wt% poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and 2 % TiO2 nanoparticles. The conductivity of PGE with P25 reached 9.98 × 10−3 S/cm, which increased by 34.9 % compared with 7.40 × 10−3 S/cm of PGE without P25, and the diffusion coefficient was also increased by 19.0 %. Different photoelectrodes were obtained by using three kinds of surfactants (cetylamine, octadecylamine, and P123) as pore-forming materials, and their morphologies were contrasted through scanning electron microscopy (SEM). The results showed that gel electrolyte can increase the short-circuit current density (Jsc) from 11.01 to 12.99 mA/cm2 in DSSCs. Moreover, unlike the liquid electrolyte, the gel electrolyte is more conducive to the TiO2 photoelectrodes with larger pores. In conclusion, the efficiency of DSSC with gel electrolyte and P123 as pore-forming material was 6.73 %, which was 12 % higher than the liquid electrolyte in the same test condition. In addition, the sealed gel electrolyte DSSCs showed better stability than did liquid electrolyte DSSCs during nearly 600 h.

Electron Transport in Quasi‐Two‐Dimensional Porous Network of Titania Nanoparticles, Incorporating Electrical and Optical Advantages in Dye‐Sensitized Solar Cells

The integration of fast electron transport and large effective surface area is critical to attaining higher gains in the nanostructured photovoltaic devices. Here, we report facilitated electron transport in the quasi-two-dimensional (Q2D) porous TiO2 . Liquid electrolyte dye-sensitized solar cells were prepared by utilizing photoanodes based on the Q2D porous substructures. Due to electron confinement in a microscale porous medium, directional diffusion toward collecting electrode is induced into the electron transport. Our measurements based on the photocurrent and photovoltage time-of-flight transients show that at higher Fermi levels, the electron diffusion coefficient in the Q2D porous TiO2 is about one order of magnitude higher when compared with the conventional layer of porous TiO2 . The results show that microstructuring of the porous TiO2 leads to an approximately threefold improvement in the electron diffusion length. Such a modification may considerably affects the electrical functionality of moderate or low performance dye-sensitized solar cells for which the internal gain or collection efficiency is typically low.

Introduction of Three-Dimensionally Distributed Catalytic Sites to Form Semi-Solid Redox Conducting Electrolytes: Enhancement of Electron Transfers within Iodine/Iodide Mediating System

It is well known that performances of dye-sensitized solar cells(DSSCs) reach their best when the cells have liquid electrolytes. However, commercialization of these cells has been impeded owing to the technological problems related to hermitic sealing, precipitation of salts at low temperature, evaporation of liquids at high temperature, corrosion, and lack of long-term stability. Replacing liquid electrolytes in DSSCs with solid or quasi-solid electrolytes is expected to make the cells viable. The promising material to replace the liquid electrolytes are ionic liquids. They possess unique properties such as high chemical and thermal stability, relative non-flammability and wide electrochemical window. Among disadvantages of ionic liquids is their high viscosity that certainly contributes to the low mass transport coefficient of the triiodide/iodide redox couple, not only if the charge transport mechanism is predominantly physical at low concentrations but also when the Grotthus exchange mechanism is operative at high concentrations of the redox system. To increase rates of electron hoping between I- and I3 -, the appropriate catalytic sites must be introduced to achieve fast dissociation of iodine (I2), or triiodide (I3 -), molecule. In other words, there is a need to develop means of inducing the I-I bond breaking and to significantly accelerate bulk electron transfers and overall charge propagation. It has also been well-established that platinum (e.g. when deposited on the counter electrode) induces electron transfers within the iodine/iodide redox system. Surface chemistry data provide clear evidence that iodine chemisorbs readily on platinum, other noble metals, certain carbon or metal oxide nanostructures as monoatomic iodine. Formation of the monolayer type coverages of strongly adsorbed monoatomic iodine together with weakly bound electroactive iodine/iodide was also postulated. In the present work, we explore the concept of using Pt [1] or Pd, which are three-dimensional distributed in the electrolyte phase (at 2% weight level) to enhance dynamics of the iodine/iodide electron self-exchange and develop a new generation of iodine-based ultra-fast charge relays for DSSC. The diagnostic experiments have been performed using the electroanalytical methodology developed for solid-state electrochemical measurements in the absence of external liquid supporting electrolyte. They have included measurements using the planar three-electrode cell utilizing an ultramicrodisk electrode and two-electrode type sandwich configuration. We have also characterized our arrangement by TEM images and zeta potential measurements. The obtained results have broader meaning than application in DSSCs. They provide means of fabricating systems capable of very fast charge propagation of importance in nanoelectronics, charge staorage and sensing. [1] I. A. Rutkowska, M. Marszalek, J. Orlowska, W. Ozimek, S. M. Zakeeruddin, P. J. Kulesza, M. Graetzel,ChemSusChem 8 (2015) 2560.

Model-Guided Design and Optimization of Polymer-Electrolyte Dye Sensitized Solar Cells

Dye sensitized solar cells (DSSCs) are commonly regarded as a promising next generation solar cell technology because they have good performance at ~13% and can be made relatively inexpensively without intensive purification and fabrication steps. However, the liquid electrolyte of conventional DSSCs is prone to leakage and evaporation, which hinders DSSC applications, durability, and thermal stability. In addition, liquid electrolytes lead to significant electron recombination at the TiO2-electrolyte interface within the cells that limit DSSC performance. Novel polymer electrolyte DSSCs can overcome these disadvantages and can potentially enhance the cell I-V behavior. Experimental studies have demonstrated that polymer electrolytes are good alternatives to liquid electrolytes in DSSCs but efficiencies are less than half of liquid-electrolyte DSSCs. Furthermore, much of the current material research in this area has been based on scientific intuition and trial and error experimentation—a slow and inefficient process with many of the directions taken to address device challenges being out without theoretical guidance. There have been relatively few studies that combine experimental and computational/theoretical approaches to better understand DSSC processes and optimize DSSC performance. Currently, there is a need for a better understanding of the effect of polymer electrolyte chemistry on cell performance. First-principles mathematical DSSC models can prove valuable in gaining this insight. By properly accounting for the physical and electrochemical processes occurring inside the cells, the models can elucidate competing effects within DSSC components, identify factors that affect the overall cell performance, and guide experimental work in designing and optimizing cell materials. In fact, many of the recent advances in the DSSC fields have relied on the computational design and screening of materials. In our previous work [1], we theoretically and experimentally investigated the effects of polymer-electrolyte chemistry on the performance of polymer-electrolyte DSSCs. To gain a complete understanding of the photochemical processes inside the DSSCs, a first-principles macroscopic model was developed and integrated with experiments that utilized initiated chemical vapor deposition (iCVD) to synthesize and incorporate the polymer electrolytes within the mesoporous TiO2 photoanode. iCVD relies on the vapor delivery of monomer and initiator, which facilitates infiltration into the porous TiO2 substrate. By controlling the relative rates of diffusion and surface polymerization through iCVD process parameters, iCVD has the advantage of being able to conformally deposit thin films within the photoanode, which has 10-20 nm pores, high aspect ratios <1000, and a tortuous pore structure. Furthermore, iCVD overcomes the challenges of liquid deposition techniques such as liquid surface tension, poor wettability, and solute steric hindrance. This enables good interfacial contact at the TiO2 electrode and polymer electrolyte junction. The model has been used to elucidate the effects of polymer chemistry on the cell performance, and to determine how and why the photochemical processes inside such solar cells are altered by poly(2‐hydroxyethyl methacrylate) (PHEMA), poly(glycidyl methacrylate) (PGMA), and poly(4-vinylpyridine) (P4VP). By varying the polymer electrolyte chemistry, the work show that DSSC cell characteristics, including open circuit voltage, short circuit current density, and fill factor can be tuned. Parameter estimation using the macroscopic model indicated that a shift in the conduction band of TiO2 and a suppression of the back electron transfer at the dye-TiO2-electrolyte interface are induced by the methyl ester of PGMA, the pyridine group of P4VP, and the hydrophilic pendant group of PHEMA. The model revealed that (a) a more favorable Lewis acid-base interaction between the polymer electrolyte and TiO2 electrode reduces charge recombination at the interface and thus leads to a higher short-circuit current, J sc, and (b) a more preferential Li+ ion (present in the electrolyte) coordination with the polymer electrolyte leads to a higher TiO2 conduction band potential and in turn to a higher open-circuit voltage, V oc. Based on this understanding, a new polymer electrolyte, poly(1-vinylimidazole) (PVIZ) which has strong basic character and metal ion chelation, is selected as a highly strong candidate for producing DSSCs that would yield higher J sc and V oc simultaneously. Our prior studies of different polymer electrolytes yielded only an increase in J sc or V oc but not in both. To experimentally validate our model’s predictions, PVIZ has been conformally integrated into the mesoporous TiO2 photoanode via iCVD. Experimental results indicate that DSSCs incorporating PVIZ have 27% greater power conversion efficiency than liquid-electrolyte DSSCs, and have a higher J sc and V oc, confirming the model predictions. To our knowledge, this is the first demonstration of PVIZ as a polymer-electrolyte in DSSCs and highlights the importance of mathematical modeling in improving the solar technology. [1] Y.Y. Smolin et al., Journal of Power Sources, 274 (2015) 156-164.

Novel Quasi-Solid-State Electrolyte Based on γ-Butyrolactone and Tetrapropylammonium Iodide for Dye-Sensitized Solar Cells Using Fumed Silica as the Gelling Agent

Dye-sensitized solar cells (DSCs) have emerged recently as low-cost photovoltaic devices, giving impressive photovoltaic conversion efficiencies. However, the use of organic solvent-based liquid electrolytes in DSCs arises many problems in long-term applications. To overcome the drawbacks associated with the liquid electrolytes, quasi-solid-state electrolytes have been introduced. Hence, this study is focused on preparation of a novel gel electrolyte system using fumed silica as the gelling agent, γ-butyrolactone (γ-BL) as the plasticizer, tetrapropylammonium iodide (Pr4N+I−) as the salt and iodine. DSCs were assembled according to the configuration of glass/FTO/TiO2/dye (N719)/gel electrolyte/Pt/FTO/glass. The cell performances have been studied, by varying the amounts of Pr4N+I− salt and plasticizer in the gel electrolyte, in order to obtain the optimum conditions. The gel electrolyte containing weight percentages of 77% of γ-BL and 23% of Pr4N+I− salt gave the best light-to-electricity conversion efficiency of 6.33%, saturated current density of 15.7mA cm-2 and open circuit voltage of 0.636V under simulated AM 1.5 irradiation. Here, I-:I2 molar ratio was kept at 10:1 in the optimized gel system and fumed silica was added 10% of the total mass. The optimized gel composition is exhibited an ionic conductivity of 8.69×10-3 S cm-1 at 25 oC.

Meso-substituted porphyrins for dye-sensitized solar cells.

Among the several approaches for harnessing solar energy and converting it into electricity, dye-sensitized solar cells (DSSC) represent one of the most promising methods for future large-scale power production from renewable energy sources. In these cells, the sensitizer is one of the key components harvesting solar radiation and converting it into electric current. The electrochemical, photophysical, and ground and excited state properties of the sensitizer play an important role for charge transfer dynamics at the semiconductor interface. Moreover, for long-term stability and practical applications, electrolytes based on the iodine/triiodine couple also suffer from two other disadvantages: the corrosive effect toward the metal electrodes, and the partial absorption of the visible light by triiodine anions. These issues hence constitute one of the reasons that have encouraged the development of alternative iodine-free redox couples in liquid electrolytes for DSSCs.

Effect of single-wall carbon nanotubes on the properties of polymeric gel electrolyte dye-sensitized solar cells

A hybrid of polymer/dispersed single-wall carbon nanotubes was utilized in networking a novel composition of gel electrolyte in dye-sensitized solar cells. The gel is composed of polyethylene glycol, polyvinyl pyrrolidone, single-wall carbon nanotubes, and I−/I3− as electrolyte. Formation of the less conductive polyiodide species in electrolyte was prohibited by the addition of single-wall carbon nanotubes leading to the excellent photovoltaic behavior of the cell under simulated standard illumination of the fabricated device owing to the increased open circuit voltage (0.47 V). Electrochemical impedance spectroscopy was employed to quantify the charge transport resistance and the electron lifetime at the TiO2 conduction band. Charge transport resistances at the TiO2/dye/electrolyte interface were determined for the cells consisting of the non-gel reference and our new gel electrolytes, and it was indicated that the charge recombination between injected electrons and electron acceptors (I3−) in the redox electrolyte was remarkably retarded. Electrochemical parameters obtained by the fitting showed all of the resistances increased as compared to liquid electrolyte dye-sensitized solar cells that can be related to the increase in viscosity of the gel, which hinders the ionic transportation through the electrolyte. These results were also confirmed by the electron lifetime analyses. The characteristic peak shifted to a lower frequency in the Bode phase plot for the cell containing gel electrolyte which is an indication of a longer electron lifetime in comparison with that of the cell containing very conventional liquid electrolyte.

Novel Ru(ii) sensitizers bearing an unsymmetrical pyridine-quinoline hybrid ligand with extended π-conjugation: synthesis and application in dye-sensitized solar cells

Heteroleptic ruthenium(II) sensitizers DV42 and DV51, encompassing a novel unsymmetrical pyridine-quinoline hybrid ligand with extended π-conjugation, were synthesized, characterized, and utilized in nanocrystalline dye-sensitized solar cells. Due to the extended conjugation of DV42 and DV51, the absorption of the corresponding sensitized TiO2 films extends into the red spectral range, shifted by 30-40 nm relative to the absorption of TiO2 films sensitized with the standard Z907 ruthenium(II) dye. Contact angle measurements of DV42- and DV51-sensitized TiO2 films suggest that these films are hydrophilic with contact angle values commonly observed upon sensitization with the standard N3 ruthenium(II) dye. Electrochemical studies of the novel ruthenium(II) dyes show that their first oxidation potentials lie well below the I(-)/I3(-) redox potential allowing easy regeneration. The excited-state oxidation potentials of both dyes lie above the TiO2 conduction band, permitting efficient electron injection from the excited dye molecules into the semiconductor conduction band. Liquid electrolyte dye-sensitized solar cells incorporating DV42- or DV51-sensitized TiO2 photoelectrodes afford overall power conversion efficiencies of 3.24 or 4.36% respectively. These efficiencies are up to 56% of the power conversion efficiencies attained by TiO2 photoelectrodes sensitized by the benchmark Z907 ruthenium(II) dye under similar experimental conditions.

Imidazolium functionalized cobalt tris(bipyridyl) complex redox shuttles for high efficiency ionic liquid electrolyte dye-sensitized solar cells

CoII/III redox couples and their derivatives have been extensively studied and applied as redox mediators for high efficiency organic solvent DSSCs. However, CoII/III complex redox mediator-based ionic liquid electrolyte DSSCs have not been studied so far due to the poor solubility of most CoII/III complexes in ionic liquid electrolytes. Herein, an imidazolium functionalized cobalt tris(bipyridyl) complex redox mediator ([Co((MeIm-Bpy)PF6)3]2+/3+) (((MeIm-Bpy)PF6)3 = 3,3′-(2,2′-bipyridine-4,4′-diyl-bis(methylene))bis(1-methyl-1H-imidazol-3-ium)hexafluorohosphate) with high redox potential and good solubility in ionic liquid electrolyte has been synthesized and applied in ionic liquid electrolyte DSSCs. Using the dye N719 as the photosensitizer, overall power conversion efficiencies of 7.37% and 8.29% are achieved in binary ionic liquid-based electrolyte under 1.5 solar spectrum illumination at 100 and 50 mW cm−2, respectively. Both values are considerably higher than those of the I−/I3− redox couple-based ionic liquid electrolyte.

The Role of π Bridges in High‐Efficiency DSCs Based on Unsymmetrical Squaraines

A series of squaraine-based sensitizers with various π bridges and anchors were prepared and examined in dye-sensitized solar cells. The carboxylic anchor group was attached onto a squaraine dye through π bridges with and without an ethynyl spacer. DFT studies indicate that the LUMO is delocalized throughout the dyes, whilst the HOMO resides on the squaraine core. The dye that incorporates a 4,4-di-n-hexyl-cyclopentadithiophene group that is directly attached onto the π bridge, JD10, exhibits the highest power conversion efficiency in a DSC; this result is attributed, in part, to the deaggregative properties that are associated with the gem-di-n-hexyl substituents, which extend above and below the π-conjugated dye plane. Dye JD10 demonstrates a power-conversion efficiency of 7.3% for liquid-electrolyte dye-sensitized solar cells and 7.9% for cells that are co-sensitized by another metal-free dye, D35, which substantially exceed the performance of any previously tested squaraine sensitizer. A panchromatic incident-photon-to-current-conversion efficiency curve is realized for this dye with an excellent short-circuit current of 18.0 mA cm(-2). This current is higher than that seen for other squaraine dyes, partially owing to a high molar absorptivity of >5,000 M(-1) cm(-1) from 400 nm to the long-wavelength onset of 724 nm for dye JD10.

Effect of Deoxycholic Acid on the Performance of Liquid Electrolyte Dye-Sensitized Solar Cells Using a Perylene Monoimide Derivative

The effect of coadsorption with deoxycholic acid (DCA) on the performance of dye-sensitized solar cell based on perylene monoimide derivative (PCA) as sensitizer and liquid electrolyte had been investigated. The current-voltage characteristics under illumination and incident photon to current efficiency (IPCE) spectra of the DSSCs showed that the coadsorption of DCA with the PCA dye results in a significant improvement in short circuit photocurrent and slight increase in the open circuit photovoltage, which lead to an overall power conversion efficiency. The enhancement of short circuit current was attributed to the increased electron injection efficiency from the excited state of PCA into the conduction band of TiO2and charge collection efficiency. The current-voltage characteristics in dark indicates a positive shift in the conduction which also supports the enhancement in the photocurrent. The coadsorption with DCA suppressed charge recombination as indicated from the electrochemical impedance spectra and thus improved the open circuit photovoltage.

The Function of a TiO2 Compact Layer in Dye-Sensitized Solar Cells Incorporating “Planar” Organic Dyes

We present a device based study into the operation of liquid electrolyte dye-sensitized solar cells (DSSC's) using organic dyes. We find that, for these systems, it is entirely necessary to employ a compact TiO2 layer between the transparent fluorine doped SnO2 (FTO) anode and the electrolyte in order to reduce charge recombination losses. By incorporation of a compact layer, the device efficiency can be increased by over 160% under simulated full sun illumination and more than doubled at lower light intensities. This is strong evidence that the more widely employed ruthenium based sensitizers act as to "insulate" the anode against recombination losses and that many planar organic dyes employed in DSSC's could greatly benefit from the use of a compact TiO2 blocking layer. This is in strong contrast to DSSC's sensitized with ruthenium based systems, where the introduction of compact TiO2 has only marginal effects on conversion efficiencies.

Novel quasi-solid electrolyte for dye-sensitized solar cells

A novel alkyloxy-imidazole polymer was prepared by in situ co-polymerization of alkyloxy-imidazole and diiodide to develop an ionic polymer gel electrolyte for quasi-solid dye-sensitized solar cells (DSCs). The DSCs with the polymer gel electrolyte of 1-methyl-3-propylimidazolium iodide (MPII) showed good photovoltaic performance including the short-circuit photocurrent density ( J sc) of 3.6 mA cm −2, the open-circuit voltage ( V oc) of 714.8 mV, the fill factor (FF) of 0.60 and the light-to-electricity conversion efficiency ( η) of 1.56% under AM 1.5 (100 mW cm −2). As a comparison, the DSCs with the polymer gel electrolyte of 1,2-dimethyl-3-propylimidazolium iodide (DMPII) yielded a light-to-electricity conversion efficiency of 1.33%. The results indicated that the as-prepared polymers were suitable for the solidification of liquid electrolytes in DSCs.

Novel polymer electrolytes containing chemically crosslinked gelators for dye‐sensitized solar cells

AbstractNovel polymer electrolytes based on ionic liquid with no volatile solvents containing chemically crosslinked gelators were prepared for quasi‐solid dye‐sensitized solar cells (DSCs). The polymer electrolytes can keep over 90% of the ionic liquid electrolyte performance. The two constituents of the chemically crosslinked gelators, polypyridyl‐pendant dendritic derivatives and multifunctional halogen derivatives, respectively, are suitable for solidification of ionic liquid electrolytes in DSCs by in situ polymerization. The ionic conductivity and photoelectrochemical performances of different polymer electrolytes were evaluated and discussed. Copyright © 2006 John Wiley &amp; Sons, Ltd.